Hexagonal Nanoparticles Research Articles

Gold Nanoparticles; Synthesis, Characterization and Comparative Studies of Their Antimicrobial Activities

Gold nanoparticles of various morphologies have been synthesized using different synthetic approaches. Sonochemical synthesis results in the formation of 25 nm sized gold nano discs and 30 nm sized polyhedral structures with surface area of 179.5 m2/g and 150.5 m2/g respectively[1]. The UV-Visible spectrum shows the SPR peaks due to in plane and out of plane excitation modes. Microemulsion synthesis using Tergitol NP-9 surfactant resulted in the production of hexagonal gold nanoparticles (avg. size: 20 nm) at 0.05 M HAuCl4 (aq) and spherical morphologies with an average size of 25 nm and 15 nm at molar concentrations of 0.04 M and 0.03 M HAuCl4 (aq) respectively[2]. Gold nanoparticles show the surface plasmon resonance peaks at 540 nm and 580 nm along with peaks corresponding to higher order plasmon resonance modes at shorter wavelengths. The surface area was found to increase with decrease in particle size. An ecofriendly synthetic route was also employed to synthesize gold nanoparticles using candida albicans fungal cell free extract[3]. Gold nanocrystals of 5 nm have been obtained with specific surface area of 18.9 m2/g. The encapsulation of gold nanoparticle by biomolecules of the cell free extract was confirmed by FTIR and TGA studies. Gold nanoparticle show surface plasmon resonance (SPR) peak at 540 nm. Gold nanoparticles have been tested for antimicrobial activity against fungal and bacterial species. Gold nano discs displayed higher antimicrobial action against fungus candida albicans as compared to gold polyhedral structures by inhibiting H+-ATPase activity. Biosynthesized gold nanoparticles showed good antimicrobial activity against Staphylococcus aureus and Escherichia coli. However, Escherichia coli, a gram-negative bacterium was found to be more susceptible to gold nanoparticles as compared to Staphylococcus aureus, a gram-positive bacterium. The microemulsion synthesized gold nanoparticles were tested against Candida albicans both alone and in combination with fluconazole. The gold nanoparticles in combination with fluconazole showed maximum inhibition and the antifungal activity increased with decrease in particle size.

Mitoxantrone in synergism with gold hexagonal nanoparticles and gamma radiation for effective treatment of MCF7 cells

Biocompatible cross-linked chitosan nanoparticles comprising the cancer chemotherapeutic drug (mitoxantrone, MX) and the novel radiosensitizer hexagonal gold nanoparticles (HG) were prepared and characterized. The prepared nanoparticles were applied, in synergism with external γ-radiation, as dual (chemo-radio) model for treatment of human breast cancer cell (MCF-7). In vitro studies revealed that HG significantly enhances the response of MCF-7 to low and moderate doses of γ-radiation (2 and 4 Gy). Cell viability assay demonstrated the synergistic anticancer actions of mitoxantrone chemotherapy and gold-sensitized γ-radiation therapy. The prepared combinatorial model is potential for efficient and safer treatment of MCF7 cancer cells.

Efficient adsorption of methylene blue on hybrid structural phase of MoO3 nanostructures

Mixed phase molybdenum oxide (mp-MoO3) nanocomposite (NC) along with hexagonal (h-MoO3) and orthorhombic (o-MoO3) nanoparticles (NPs) were synthesized via easy and cost-effective internal combustion method using water/ethanol mixture, water, and methanol solvents. The formation mechanisms of h-MoO3, o-MoO3, and mp-MoO3 have been investigated using different physical methods such as XRD (X-ray diffraction), FTIR (fourier transform infrared spectroscopy), FESEM (field emission scanning electron microscopy), HRTEM (high resolution transmission electron microscopy, and SAED (selected area electron diffraction). The potential of prepared NPs and NC on the adsorptive removal of methylene blue (MB) was investigated through the adsorption batch process with variation in the adsorbent dosage, pH, and temperature of the solution. The confirmation of dye adsorption over adsorbent surfaces has been elucidated by employing FTIR and FESEM after the adsorption process. The influence of different NPs and NC on the adsorption efficiency indicates the possibility of physical, chemical as well as electrostatic interaction between adsorbent-adsorbate interface. Thermodynamical parameters were calculated and analyzed for the validity of the adsorption phenomenon. Various kinetic study models such as pseudo-first-order (PFO), pseudo-second-order (PSO), and Intra-particle diffusion (IPD) were fitted to the experimental data to explore the rate-controlling step and for understanding the adsorption mechanism. The mp-MoO3 NC was observed to have the best adsorption efficiency as well as a better adsorption rate. Therefore synthesized mp-MoO3 NC showed great potential for dye adsorption and would be seen as the futuristic adsorbent materials for sustainable water treatment technology.

Optical neural stimulation using the thermoplasmonic effect of gold nano-hexagon.

The use of nanoparticle photothermal effect as adjuvants in neuromodulation has recently received much attention, with many open questions about new nanostructures' effect on the action potential. The photothermal properties of hexagonal gold nanoparticles are investigated in this work, including the absorption peak wavelength and light-heat conversion rate, using both experimental and simulation methods. Furthermore, the ability to use these nanostructures in axonal neural stimulation and cardiac stimulation by measuring temperature changes of gold nano-hexagons under 532 nm laser irradiation is studied. In addition, their thermal effect on neural responses is investigated by modeling small-diameter unmyelinated axons and heart pacemaker cells. The results show that the increase in temperature caused by these nano-hexagons can successfully stimulate the small diameter axon and produce an action potential. Experiments have also demonstrated that the heat created by gold nano-hexagons affects toad cardiac rhythm and increases T wave amplitude. An increase in T wave amplitude on toad heart rhythm shows the thermal effect of nano hexagons heat on heart pacemaker cells and intracellular ion flows. This work demonstrates the feasibility of utilizing these nanostructures to create portable and compact medical devices, such as optical pacemakers or cardiac stimulation.

Sensitive Simultaneous Detection of Methyldopa and Hydrochlorothiazide on Ce3+-NiO Hexagonal Nanoparticles-Modified Electrode

We applied GCE modified with Ce3+-NiO hexagonal nanoparticles (Ce3+-NiO HNPs) for preparing methyldopa electrochemical sensor. Electrochemical study of the modified electrode showed that within the optimal conditions of phosphate buffer solution (PBS) at a pH of 7.0 in CV, oxidation potency of methyldopa decline to ~100 mV at the modified electrode in comparison with an unmodified GCE. The sensor exhibits a sensitive response to methyldopa in range between 0.1 and 80.0 μM with a limit of detection (LOD) equal to 0.03 μM. In addition, as sensing materials for simultaneously determine hydro-chlorothiazide and methyldopa, Ce3+-NiO HNPs/GCE, exhibited high sensitivity. The defined and separated oxidation peaks of a mixture of methyldopa and hydrochlorothiazide were obtained with significant peak potential differences of 390 V. The proposed electrochemical sensor was employed in analysis of both drugs in the real specimens.

Biosynthesis and Characterization of ZnO Nanoparticles Using Ochradenus arabicus and Their Effect on Growth and Antioxidant Systems of Maerua oblongifolia.

Zincoxide nanoparticles (ZnO NPs) are among the most produced and used nanomaterials worldwide, and in recent times these nanoparticles have also been incorporate in plant science and agricultural research. The present study was planned to synthesize ZnO NPs biologically using Ochradenus arabicus leaves and examine their effect on the morphology and physiology properties of Maerua oblongifolia cultured in vitro. ZnO NPs were characterized by UV–visible spectroscopy (UV–vis), X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy, which demonstrated hexagonal shape nanoparticles of size ranging from 10 to 50 nm. Thus, the study uncovered an efficient, eco-friendly and simple technique for biosynthesis of multifunctional ZnO NPs using Ochradenus arabicus following growth of Maerua oblongifolia shoots in different concentrations of ZnO NPs (0, 1.25, 2.5, 5, 10, or 20 mg L−1) in Murashige and Skoog medium. Remarkable increases in plant biomass, photosynthetic pigments, and total protein were recorded up to a concentration of 5 mg L−1; at the same time, the results demonstrated a significant reduction in lipid peroxidation levels with respect to control. Interestingly, the levels of proline and the antioxidant enzyme catalase (CAT), superoxide dismutase (SOD), and glutathione reductase (GR) activities were increased significantly in response to all ZnO NP treatments. These findings indicate that bioengineered ZnO NPs play a major role in accumulation of biomass and stimulating the activities of antioxidant enzymes in plant tissues. Thus, green-synthesized ZnO NPs might be of agricultural and medicinal benefit owing to their impacts on plants in vitro.

Template-free, facile synthesis of nickel promoted multi-walled MoS2 & nano-bricks containing hierarchical MoS2 nanotubes from the bulk NiMo oxide

A low-temperature and template-free synthesis method was developed to prepare MoS2 nanotubes by sulfidation of bulk NiMo oxide. The ex-situ gas-phase low-pressure sulfidation of NiMo oxide resulted in multi-walled MoS2 nanotubes and NixSy spheres. Meanwhile, the in-situ liquid phase high-pressure sulfidation led to nanotubes formation by self-assembly of MoS2 nano-bricks vertically oriented towards the outer surface as observed by HRTEM analysis. The sulfided catalysts were evaluated for the hydrodesulfurization (HDS) of dibenzothiophene (DBT) in a batch reactor. Catalyst sulfided under ex-situ conditions exhibited good performance (76 % DBT conversion with an initial reaction rate 24 × 10−8 molDBT.(gCat.s)-1). The in-situ sulfided catalyst showed an outstanding activity (99 % DBT conversion with an initial reaction rate 105 × 10−8 molDBT.(gCat.s)-1). Which means that the in-situ sulfidation method dramatically increased the initial reaction rate by four times. A mathematical expression (RKC equation) was derived to correlate the size of the regular hexagonal MoS2 nanoparticles with its activity, for which the experimental results were validated.

Antibacterial and photocatalytic behaviour of green synthesis of Zn0.95Ag0.05O nanoparticles using herbal medicine extract

The present work aimed to synthesize Zn0.95Ag0.05O (ZnAgO) nanoparticles using rosemary leaf extracts as a green chemistry method. The characterization of Ag-doped ZnO nanoparticles was performed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and ultraviolet–visible spectrophotometry (UV–visible). The XRD, FTIR, and UV–visible spectra confirmed the formation of the presence of hexagonal ZnAgO nanoparticles. FESEM micrograph shows that the nanoparticles have been distributed homogeneously and uniformly. The morphology of ZnAgO nanoparticles is quasi-spherical configuration. Also, the mean particle size is in the range of 22–40 nm. The photocatalytic degradation of methylene blue in the presence of Ag-doped ZnO nanoparticles is nearly 98.5% after exposing 100 min. The ultraviolet lamp was used as the light source for photocatalyst degradation. The disc diffusion method was chosen to study the antibacterial activity of as-synthesized ZnAgO nanoparticles. Antibacterial activity of Zn0.95Ag0.05O nanoparticles against Staphylococcus aureus and Escherichia coli revealed that the as-synthesized ZnAgO nanoparticles were efficient in inhibition of bacterial growth.

CdS/BiOBr heterojunction photocatalyst with high performance for solar-light-driven degradation of ciprofloxacin and norfloxacin antibiotics

Sunlight active CdS/BiOBr heterojunction photocatalyst was fabricated by a solvothermal route. To the best of our knowledge, the novelty of the research is based on the decoration of the hexagonal CdS nanoparticles on the surface of the tetragonal BiOBr microflowers for the creation of a heterostructure photocatalyst used for the removal of the antibiotics. The CdS/BiOBr-1:3 heterojunction exhibited 100% removal of norfloxacin and ciprofloxacin under simulated visible light. In addition, complete degradation of the antibiotics under natural sunlight was also achieved. Construction of the CdS/BiOBr heterojunction is a promising strategy for the improvement of photocatalytic performance due to a decrease in the charge carrier recombination rate at the interface, an increase in the visible light absorption range, and an enhancement of the surface area of the resultant product. The removal of the pollutants fit very well with the first-order reaction. The photogenerated hole played a crucial role in the removal of the antibiotics. Confirmation of the stability of the CdS/BiOBr heterojunction was also elucidated. The photoactivity of the photocatalyst remained the same after the fifth cycle implying the excellent cycling ability of the sample. This research demonstrates the promising potential of the CdS/BiOBr heterojunction for degradation of toxic antibiotics presented in water.

Structural and spectroscopic analysis of pure phase hexagonal wurtzite ZnO nanoparticles synthesized by sol-gel

In the present study, Sol-gel route was employed to synthesize the pure phase hexagonal wurtzite zinc oxide (ZnO) nanoparticles with crystallite size and lattice strain ~ 21 nm and ~ 7.6 × 10-4 respectively. The synthesized ZnO nanoparticles were characterized by X-ray Powder Diffraction (XRPD), Fourier Transform Infrared (FTIR) Spectroscopy and Raman spectroscopy at room temperature. FTIR spectrograph demonstrates the presence of stretching vibration of Zinc-Oxygen (Zn-O) bonding. The Raman active optical phonon mode E2High at 438.59 cm−1 confirms the formation of pure phase wurtzite hexagonal ZnO nanoparticles.

Phase transitions in cadmium sulfide nanoparticles

CdS nanoparticles were synthesized by the microwave assisted chemical precipitation method and solvothermal method. X-ray power diffraction, scanning electron microscopy, and transmission electron microscopy were employed to characterize the crystalline structure, morphology, and size of the synthesized samples. X-ray diffraction studies reveal that the synthesized samples are of two different forms, cubic and hexagonal. The DC electrical resistance of the two samples was measured in the temperature range 300–500 K. Near room temperature cubic nanoparticles behave as a semiconductor, and hexagonal nanoparticles show the behavior of an insulator. The temperature resistance curves of the cubic sample show a transition from the cubic to hexagonal phase above 340 K. The temperature resistance curve of the hexagonal sample also shows a discontinuity at 463 K due to the transition from the hexagonal to cubic phase. The thermogravimetric analysis of the two samples also confirms the two transitions. UV, PL, and Raman spectra of the two forms are compared.

Mycosynthesis of silver nanoparticles using Aspergillus caespitosus: Characterization, antimicrobial activities, cytotoxicity, and their performance as an antimicrobial agent for textile materials

AbstractMycosynthesis of stable silver nanoparticles (AgNPs) using Aspergillus caespitosus exo‐ and endo‐filtrates were obtained. Both exo‐ and endo‐AgNPs showed an absorbance peak at 410 nm, spherical, hexagonal, and anisotropic crystalline nanoparticles with 22–57 nm in size. FTIR analysis of mycosynthesized AgNPs showed presence of amide and carbonyl functional groups, which depicts the presence of peptides that involved in the synthesis and stability of AgNPs. Nitrate reductase activity was found to be 0.71 and 0.36 μM/min/ml for exo‐ and endo‐filtrates, respectively. The optimum conditions for the synthesis of exo‐ and endo‐AgNPs were at 6:4 and 8:2 filtrate:double distilled water dilution, respectively. Also, both AgNPs syntheses were the maximum at using one mM AgNO3 in aqueous solution, 24‐h incubation at 30°C under static and illuminating conditions. Aspergillus caespitosus‐synthesized AgNPs showed antimicrobial activities against Gram‐positive and Gram‐negative bacteria and Candida albicans. They showed non‐cytotoxic effect with exception of endo‐AgNPs on MCF‐7 breast carcinoma cells. Different textile samples treated with these nanoparticles exhibited antimicrobial activities against the tested pathogenic microorganisms. Finally, Aspergillus caespitosus is a promising nano‐factory for simple, green, and cost‐effective biosynthesis of AgNPs using extracellular and intracellular filtrates.

Green synthesis of zinc oxide nanoparticles by Ziziphus jujuba leaves extract: Environmental application, kinetic and thermodynamic studies

This research reports, for the first time, the eco-friendly green synthesis of zinc oxide nanoparticles (ZnO NPs) using Ziziphus jujuba leaves extract assisted by microwave irradiation. Eco-friendly prepared ZnO NPs were characterized by different techniques, and the results confirmed the formation of hexagonal wurtzite ZnO nanoparticles with different particle sizes. The prepared ZnO NPs were then used for the adsorption and removal of two different azo dyes; methyl orange (MO), and methylene blue (MB), as well as toxic Pb(II) ions, from a model solution and real samples. The influence of experimental conditions was explored; ZnO NPs mass, contact time, solution pH, solution ionic strength, and solution temperature, and the results showed that most of the MB, MO, and Pb(II) could be removed from the model solution within a few minutes, at ambient conditions. The experimental removal capacities of 5.21, 2.57, and 596 mg of MO, MB, and Pb(II) per gram of microwave-assisted green ZnO NPs (MWG ZnO NPs), respectively, were obtained. The removal of the MB, MO, and Pb(II) using ZnO NPs was studied kinetically and thermodynamically, and the results showed that the experimental data were best fitted using the pseudo-second-order kinetic models, with rate constants of 0.165, 0.364, 247 × 10–6, for the MO, MB, and Pb(II), respectively. The thermodynamics study showed that the process was spontaneous, with an exothermic nature. Finally, the prepared ZnO NPs were used for the removal of MB, MO, and Pb(II) in real wastewater samples, and high removal efficiency was presented. The regeneration and reusability were explored, and the results revealed the applicability of using the MWG ZnO NPs for the removal of MB, MO, and Pb(II) for five consecutive cycles.

Enhanced photocatalytic degradation of Acid Blue 1 using Ni-Decorated ZnO NPs synthesized by sol-gel method: RSM optimization approach

In this research, the synthesis of pure and Ni-decorated ZnO nanoparticles was carried out successfully by sol-gel method. The morphology, structure, chemical bonding, and absorption spectrum of the synthesized nanoparticles were investigated using FESEM, TEM, XRD, EDX and elemental mapping, FT-IR, and UV–Vis techniques. After Ni decoration, the spherical structure of ZnO nanoparticles almost changed to uniform hexagonal nanoparticles. The synthesized nanoparticles were used for Acid Blue 1 dye degradation through a photocatalysis procedure under UV light (6 w). The influence of four factors, including metal (Ni) percentage, dye concentration, catalyst dosage, and pH, on the photocatalytic activity of the synthesized photocatalysts, was studied. The experiments were evaluated by means of the response surface methodology (RSM) based on the central composite design (CCD). The experimental results indicated dye concentration = 10 mg/L, pH = 7.77, Ni percentage = 1.117% and catalyst dosage = 1.07 g/L as the optimum values for variables. At optimum conditions, CCD estimated the degradation rate equal to 90.23% which is close to the experimental efficiency, 89.13%, (R2 = 0.9877 and adjusted R2 = 0.9762). The results confirmed the reliability of the CCD to predict the amount of dye removal. Additionally, the Ni-decorated ZnO nanoparticles had more activity in the visible area than the pure ZnO sample. According to the UV–Vis spectra, the band gap decreased from 3.13 to 2.97 eV by adding Ni to ZnO. Furthermore, the Ni-decorated ZnO sample represented a significant redshift compared to the pure sample.

Thermodynamic properties and hysteresis loops in a hexagonal core-shell nanoparticle

We applied Monte Carlo simulation to investigate the thermodynamic properties and hysteresis loops of the hexagonal core-shell nanoparticle described by a ferrimagnetic mixed-spin (3/2, 5/2) Ising model. The results revealed the significance of the single-ion anisotropy, exchange coupling, external magnetic field in dominating various thermodynamic quantities and hysteresis loops. We obtained the variation of the critical temperature with various parameters. Under certain parameter conditions, the system may exhibit rich multiple-loop hysteresis behaviors, depending on the competition among the physical parameters.

Serrated hexagonal ZnO Nanoparticles: Synthesis and its characterization

ZnO nanoparticles with serrated hexagonal morphology were synthesised via hydrothermal route. XRD plot affirms the ZnO nanoparticles are formed. FTIR was performed to study the various vibrational modes of the synthesised ZnO nanoparticles. UV–VIS spectra was recorded to calculate the energy band gap of ZnO nanoparticles. Electrochemical studies were performed via Electrochemical Impedance Spectroscopy and Cyclic voltammetry techniques that shows the synthesised nanoparticles are appropriate for the application in Dye-sensitized solar cells.

Experiment on Injection of SIC and BN Nanoparticles into Liquid Aluminum Using MHD Stirring with Subsequent Crystallization of the Melt

The paper describes the technique and results of experiments on the introduction of SiC and BN nanoparticles into an aluminum melt contained in a cylindrical crucible with a water-cooled bottom and heated walls. The crucible was placed in an MHD stirrer, which generated a travelling and rotating magnetic fields ensuring in such a way bidirectional stirring of the liquid metal in the crucible. After introducing the reinforcing particles, aluminum was stirred and directionally crystallized. Reinforcing particles were introduced into molten aluminum as a component of pressed pellets. Pellets with diameter of 20 mm and thickness of 15 mm were made from a mixture of aluminum powder (100-156 µm) and reinforcing nanoparticles (100-200 nm) by pressing in a special pellet die. The concentration of reinforcing particles in the pellets was selected using preliminary experiments and was 5% of their total weight. In some experiments, the aluminum was reinforced with SiC nanoparticles introduced into the melt in the amount of 0.59%, 1.04%, 1.77%, while in other experiments the concentration of hexagonal BN nanoparticles introduced into aluminum was 7%, 1%, 1.8% of the ingot weight. As the experiment showed, the reinforcing particles formulated into tablets can be introduced into aluminum by means of MHD stirring. The dependence of the ultimate strength and electrical resistance of aluminum on the concentration of the reinforcing nanoparticles introduced into it has been obtained experimentally. It has been found that with an increase in the concentration of nanoparticles in aluminum, its ultimate strength and specific electrical resistance increase. The dependences of the ultimate strength and electrical resistance of aluminum on the concentration of SiC and BN nanoparticles are very similar and close to linear (in the investigated range of concentrations of introduced particles. With an increase in the concentration of introduced nanoparticles the mechanical strength of the resulting material grows faster than the electrical resistivity. In the experiments, the ultimate strength of the samples increased by 22%, while the electrical resistance increased by 5-6%. This opens up new possibilities for industrial applications of such materials, for example, in manufacture of self-supporting wires in power lines.

Photocatalytic behavior of Ba(Sb/Ta)2O6 perovskite for reduction of organic pollutants: Experimental and DFT correlation

We have synthesized closely packed hexagonal 2D plates and clustered nanoparticle morphologies of Ba(Sb/Ta)2O6 (BSTO) perovskite via the polymerizable complex method for photocatalytic dye degradation activities. The BSTO crystallized in a hexagonal structure. The presence of Ba2+, Sb5+, Ta5+, and O2− chemical states identified from XPS confirmed the formation of mixed Ba(Sb/Ta)2O6 phase accompanied with a minor amount of TaOx. Furthermore, BSTO showed excellent photocatalytic activity for the degradation of various organic dyes. The kinetic studies revealed 65.9%, 77.3%, 89.8%, and 84.2%, of Crystal Violet (CV), Methylene Blue (MB), Rhodamine blue (RhB), and Methylene Orange (MO), respectively, after irradiation of 180 min without using a cocatalyst. The formation of O2− and OH−surface radicals, which are believed to facilitate the degradation of the dyes, are unveiled through first-principles Density Functional Theory (DFT) calculations and scavenging studies. Our results suggest that BSTO holds promise as an excellent photocatalyst with better degradation efficiency for various organic dyes.

Polyol mediated synthesis of hexagonal manganese cobaltate nanoparticles for voltammetric determination of thioridazine

A polyol mediated synthesis method is proposed as a good crystallinity, high sensitivity, and efficient fabrication route to synthesize hexagonal manganese cobaltate nanoparticles (MnCo2O4) using ethylene glycol as a reducing and stabilizing agent. The structural and morphological study was examined by X-ray diffraction (XRD), Raman spectroscopy, fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy (EDX) analysis. The electrocatalytic performance of as-prepared nanoparticles drop cast on the glassy carbon electrode. Under optimized voltammetric conditions, the as-proposed sensor shows good performance towards thioridazine (TZ) oxidation with a linear range from 0.2 to 1119 μM, a low detection limit of 0.021 μM. The fabricated MnCo2O4 electrode sensitivity was calculated to be 1.872 µA µM–1 cm2. The practical applicability of the sensor exhibits good stability, repeatability, reproducibility, and selectivity in the presence of 15-fold concentrations of metal ions and organic compounds for the TZ detection. The real-time analysis of fabricated electrode was applied to detect TZ in human serum samples and gave satisfactory results.

Polymer Nanocomposites for Photocatalytic Degradation and Photoinduced Utilizations of Azo-Dyes.

Specially designed polymer nanocomposites can photo-catalytically degrade azo dyes in wastewater and textile effluents, among which TiO2-based nanocomposites are outstanding and extensively explored. Other nanocomposites based on natural polymers (i.e., chitosan and kaolin) and the oxides of Al, Au, B, Bi, Fe, Li, and Zr are commonly used. These nanocomposites have better photocatalytic efficiency than pure TiO2 through two considerations: (i) reducing the hole/electron recombination rate by stabilizing the excited electron in the conducting band, which can be achieved in TiO2-nanocomposites with graphene, graphene oxide, hexagonal boron nitride (h-BN), metal nanoparticles, or doping; (ii) decreasing the band energy of semiconductors by forming nanocomposites between TiO2 and other oxides or conducting polymers. Increasing the absorbance efficiency by forming special nanocomposites also increases photocatalytic performance. The photo-induced isomerization is exploited in biological systems, such as artificial muscles, and in technical fields such as memory storage and liquid crystal display. Heteroaryl azo dyes show remarkable shifts in photo-induced isomerization, which can be applied in biological and technical fields in place of azo dyes. The self-assembly methods can be employed to synthesize azo-dye polymer nanocomposites via three types of interactions: electrostatic interactions, London forces or dipole/dipole interactions between azo dyes, and photo alignments.